Display elements of image display devices such as television receivers have recently been shifting from conventional CRTs to thin display devices that use thin display elements such as liquid crystal panels and plasma display panels. This makes it possible for image display devices to be thinner. Since the liquid crystal panels used in liquid crystal display devices do not emit light, a backlight device is additionally required as an illumination device.
Conventionally, edge-lit backlight devices with light entrance surfaces provided on side surfaces of a light guide plate, and light sources such as LEDs arranged on sides of the side surfaces of the light guide plate, are known as one example of a backlight device. Disclosed in Patent Document 1 is an edge-lit backlight device with light sources arranged in three directions around the side surfaces of the light guide plate in order to enhance brightness.